Butadiene-styrene elastomers



- elastomer.

Patented Feb. 12,

UNITED STATES-FATE BUTADIENE-STYRENE ELASTOMERS John R. Vincent, vWilmington, DeL, asslgnor to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation 01' Delaware No Drawing. Application April 29, 1944,

. SerialNo. 533,399

\- a 6 Claims.

This invention relates to a method of improving the processability oi butadiene-styrene elastomers, and has for its object the addition of materials to the butadienestyrene elastomers whereby they can be more readily and quickly processed with the machinery ordinarily employed in the processing of natural rubber.

The data wasobtained using a laboratory rub-' ber mill having rolls 6 inches long and 2 inches In attempting to replace natural rubber with the synthetic rubbers such as Buna S, G '.-s| Hycar OS 10, Hycar OS 20,'etc., which are butadiene-styrene elastomers, one of the major probv lems has been the working of such synthetic elastomers on the usual rubber. working machincry. The working of such synthetic rubbers, even where it is possible to carry it out on the usual rubber machinery, requires excessive time to etin diameter, running at the same speed. The

rolls were set 0.030 inch apart and werekept at 7011 C., during the testing.- A 5.0 g. portion of the elastomer was milled until a band "free oi: holes, for at least the time required for one revolution of the mill rolls, was obtained. The imel required for this was noted. The runfwas hen repeated with a 50 g. portion of the identical elastomer, and the salt to be tested was added to the elastomer, as quickly as possible, at the .iect the break-down or to properly compound the same with the necessary compounding materials.

, Where long periods of working are required to eifect the desired result, the volume output per unit oi" equipment is necessarily low, and the power. consumption unduly high.

Ihave found that the processabllity' or the 0.05% to ot a polyvalent metal salt of a terpene mercaptan, based on the weight of the elastomer. The addition or a small amount or such polyvalent metal salt or the terpene mercaptanof the butadiene-styrene elastomer has been found to result in a material decrease in the time 01' milling required to break down'the elastomer to a condition satisfactory for the introduction or compounding ingredients. It also results in a substantial decrease in the'time required for introducing the compounding Illustrative examples of the salts that are ef-i iectiye in reducing the milling time of a butadiene-styrenc elastomer are shown in the table below; In this case, the elastomer used was GR-S (the butadiene-styrene rubber made under the government's synthetic rubber program).

The data is for various metal salts oi'pinene meringredients into such I butadiene-styrene elastomers can be greatly improved it there is incorporated therewith from.

beginning of the run. The time'to produce-a band free of holes was again noted; By comparing the results of such a pair of runs, the improvementin milling time provided by the added salt can be expressed in terms of percentage reduction in milling time. i

These data show that these ,saltscause a marked reduction ini the milling time of GR-S.

Other metals and other'terpene mercaptans can also beused. For example, 4% oi zinc isofenchyl mercaptide results in a 38% reduction in the milling of asample of GR-S from manufacturer B, lot 2. GM from manufacturer; 0, lot'2,'was

reduced 38% in.milling time by 4% copper camphene mercaptide and 33% by 4% of copper beta-pinenemercaptide. c I

These results show that a very large saving in. time and in power may be obtained bythe use oi such salts. Further savings in time. and

'- power are obtained during the compounding op-' eration, particularly during the incorporation of a carbon black into the elastomer.

The terpene mercaptanairom whichthese salts may be made, are-obtained by the reaction or the terpene with hydrogen sulfide, as described in -U. 8. Patent. 2,076,875, or. by sulfurizing xthe terpene and then subjecting the suliurized terpene to catalytic hydrogenation over a sulfactive.hydrogenation catalyst'in accordance withthe processes disclosed in more detail in copending,applications of Fox SerialNo. 440,253 and Werntz Serial No. 440,249, both filed April 23, 1942. I

The polyvalent metal salts of the terpene mericaptans are preferably employed in an amount equal to from 0.05% to 5% oi the weight of the elastomer. These compounds are effective in reducing the milling time of the elastomer at any temperature between 25 C. and 0., and they may be introduced into the elastomer and used in aninternal mixer, as well as on a mill.

The salts of terpene mercaptans, such as sylvestrene, the m'enthenes. limonene, pseudolimonone, carvone, serene. the 'teminenes. alpha and beta. phellandrene, terplnolene, bomylene, Eelinene, mentheiene, fernesene, ienehene, isone and ionone memeptens, may also be used for this purpose. The sells with other metals. such. as

. titanium, tin cm'emlum, manganese, iron, co-

belt and antimony meg also be used.

The butadiene-styrene elasbomer may be one containing from 5% toj% o! styrene.

Iclalm: 7

1. A method for improving the pmcessing characteristics of wtedlenestyrene interpolymers centelnlng from $30 00% oi styrene. which comprises intimately incorporating in said inter= polymer from. 0.5% in 5.0%, based on the weight of the intlymer. of a, polyvalenfu metal salt of e A terpene merespeen.

2. A method for improving the processing char ecterlsties of bute/diene-styrene interpolymers s1 '1, from 5% to 60% of s'tyrene'whlch cnmprises intlelv incorporating in said interpoer from 0.5% as 5.0%, based on the weight of the intermles, @Mhe zine Belt of e. terpene memeplen. i

messes 3. A methm mim rovmg the processing cherecteristics of butadiene-styrene lnterpolymers eonteinlng from 5% la 60% of styl ene, which comprises intimately incorporating in said interpolymex from 0.5% to 5.0%, based on the weight of the lnterpolymer, of the zinc salt of pinene mercaptml .4. A buteoliene-styrene interpolymer containing from 5% to 60% of styrene having incorporated therein from 0.5% to 5.0%, based on theweight of the interpol-ymer, at a. p lyvelent metel salt of a. te 'pene mercaptan.- 4

5. A butsdiene-styrene interpolymer contain- ,ing from 5% to 60% of styrene having incomerated therein from 0.5% lo-5.0%, on the weight of theinterpolymer, of the zinc salt of e. terpene mercapten. w

6. A butadiene-styrene interpolymercontaining from 5% to of styrene having incorporated therein fll'Qm 0.5% to 5.0%, based on the weight of the interpolymer, of the zincsalt of pinene mer'ceptan.

' R. VDICENIZ. 

